The invention relates to the automatic sharpening of saw chains by the average user of the saw chain, while the chain is mounted on the saw sprocket and chain bar. For many chain saw models, especially those directed to the non-professional market, it is desirable to provide for automatic sharpening of the chains by the user without removing the chain from the saw. This is commonly provided by moving a sharpening stone or like element into contact with top-sharpenable cutter teeth of the chain while the chain is being driven by a normal operation of the saw.
While a number of prior systems have been provided which are capable of effecting automatic chain sharpening, there have been a number of drawbacks associated with prior art systems. Commonly, the mounting arrangement for such structures in order to provide the proper operational movement of the stone into contact with the chain have been relatively complex. Additionally, fine control of the movement of the stone into contact with the chain, with appropriate limiting of the extent of movement, has not been provided, resulting in undue wear to the stone and chain. Additionally, any adjustments to be made in the initial position of the stone have conventionally been continuous adjustments, making it easier to move the stone too far, again resulting in undue wear to the components, and possibly even interfering with chain operation. This is especially so since the market to which automatic saw chain sharpeners are primarily directed is, as mentioned above, the non-professional market.
According to the present invention, problems associated with conventional automatic saw chain sharpeners have been overcome, and a chain saw chain sharpener is provided that allows a controlled, repeatable, and accurate sharpening of a saw chain. The sharpener mechanism is mounted in a readily accessible, convenient manner, the sharpening stone is moved into contact with the saw chain by a (predetermined length) stroke rotary lever, adjustment of the initial position of the stone to accommodate wear is incremental, and a mode of operation is provided for returning the stone mounting structure to an original position to allow replacement of the stone after the original stone has been worn down. In general, simple and effective saw chain sharpening is provided by practicing the invention.
According to one aspect of the invention, in combination with a chain saw having a powered sharpenable chain, a chain sharpener assembly is provided. The assembly includes a sharpening stone, and means for effecting linear movement of the stone a predetermined stroke length toward and away from the chain to be sharpened so that in a first position thereof the stone is spaced from the chain, and in a second position thereof the stone operatively engages the chain. Also means for effecting incremental adjustment of the spacing of a chain-distal portion of the stone from the chain in the first position are provided.
The means for effecting linear movement of the stone effect movement in first and second opposite linear directions, toward and away from the chain, respectively. The movement effecting means comprise means for effecting movement of the stone in a first mode of operation in both the first and second directions; means for effecting movement of the stone in a second mode of operation in only the first direction; and means for effecting movement of the stone in a third mode of operation in the second direction, the modes being entirely distinct from each other. For instance by grasping the operating lever and rotating it initially in one direction, the operator moves the stone toward the chain for sharpening. By axially depressing the operating lever, and initially moving it in a second direction, opposite the first direction of rotation, and then returning the operating lever to its initial position, the operator effects an incremental adjustment of the stone toward the chain. By not using the operating lever at all, but rather by manually defeating a pawl mechanism and by using a screwdriver to rotate a central shaft coaxial with the lever, the stone can be returned to an original position.
The invention also includes a chain saw having a drive sprocket contained by a housing, a chain bar extending outwardly from the housing and disposed in a predetermined plane, and a sharpenable saw chain driven by the sprocket around the chain bar. The housing includes a side wall thereof disposed in a plane substantially parallel to the chain bar, and a sharpener assembly is mounted by the side wall and includes a sharpening stone mounted interiorly of the housing and adjacent the sprocket. The stone is mounted for reciprocal movement, and an operating lever extends outwardly from the housing and is mounted exteriorly of the housing for engagement by an operator to effect movement of the stone. The operating lever is rotatable about an axis of rotation perpendicular to the side wall, and it extends upwardly from the housing and has a distal portion that does not overlap the housing at any time during movement of the operating lever.
The invention also comprises the particular mechanical drive assembly components utilizable in the saw chain sharpener, and method of operation thereof. The components are small and very compactly arranged, yet provide three different modes of operation in an effective manner.
It is the primary object of the present invention to provide a simple and effective chain saw chain sharpener which provides a controlled, repeatable, and accurate sharpening of the saw chain. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.